1. Field of the Invention
This invention concerns tractor vehicle cab suspension embodiments.
More specifically, a tractor cab suspension system where an operator's cab or alternatively an operator's work station platform in tractors without cabs, is integrally attached to the front portion sheet metal of the tractor and the entire superstructure assembly is pivotally mounted to the forward portion of the tractor running gear frame. The rear portion of the integrated cab and front sheet material is suspended on a coil spring. A pair of vertical members coact with vertical walls of the cab subfloor extension to limit lateral movement of the integrated assembly while allowing vertical movement of the rear section on an arc generated around the front pivot point. Wheels, axially carried on the inner sides of the frame mounted vertical members, may be provided to insure unhampered movement in a vertical plane between the integrated superstructure and the tractor running gear frame.
2. Description of the Prior Art
It is known in the highway truck art to provide suspended cabs for improved ride. These cabs may be pivotally mounted at the front thereof to the vehicle frame and may also be provided with coil spring suspension system at the back section of the cab.
In the tractor art, which has more stringent and diverse cab suspension problems (vis-a-vis highway trucks) due to the general roughness of the supporting terrain, it appears that emerging technology to provide more comfortable operator environments is being centered around the suspension of the cab or operator's work area only. Generally a three or four point cab mounting system is provided. Coil spring and shock absorber systems are seen as one alternative to a diverse spectra of designs. One difficulty with these designs may often be the lateral deflection of the cab in a roll over due to the magnitude of suspension travel allowed in these designs. This problem is not presented in the instant invention as the lateral movement of the cab is restricted by the vertical uprights of a generally U-shaped member and horizontal cab deflection is restricted through the relatively close tolerance of the suspended superstructure at the forward pivot point on the front of the vehicle at the frame.
Another problem with prior art tractor vehicles having the superstructure spring mounted above the vehicle frame and running gear is that it is difficult to maintain a sealed relationship between the inside of the floating hood and the top (and sides) of the radiator as these parts separate. Current designs require an expandable dam, most generally an elastomer bellows, to maintain this sealed arrangement. This problem does not exist with the design herein described as the inner surface of the hood sheet moves only a small distance on an arcuate path around the front pivot point. The conventional dam of current production tractors flexes sufficiently to accommodate this insignificant displacement between the inside of the hood and the top and sides of the heat exchanger.
Furthermore tractor vehicles are known that have integrated cab and front sheet metal sections suspended over the vehicle frame. The only examples of these embodiments known to the inventor are tractor superstructure suspension systems where at least four suspension points are provided. Two of these suspension points are at the forward end of the vehicle and two are at the rear. No tractor vehicles of which we are aware appear to have the combination forward pivot point and rear suspension with the U-shaped guide frame of this invention.